1. Field of Invention
The invention relates to a stage for supporting, moving and positioning articles in an xy plane. More particularly, the invention relates to a stage used for supporting and positioning articles in an xy plane in an electron beam lithography system.
2. Description of the Related Art
Many devices such as reticles, semiconductor circuits and liquid crystal displays are fabricated using lithographic equipment, such as an electron beam lithography system. In the fabrication of circuits and/or liquid crystal displays, a article must be accurately and precisely positioned under the optics of a lithographic system. Such positioning is necessary to ensure accurate alignment of the microscopic features being formed in a new layer with other microscopic features in the layers previously formed on the article during the fabrication process. Also, the formed microscopic features on one article must be repeated on other articles in a repetitive process operation.
Complex systems have been developed to position an article, such as positioning a wafer substrate or a reticle, beneath lithographic optics. A step and repeat system often uses an xy positioning system to position the article on a positioning stage beneath the lithographic equipment, expose a portion of the article to a pattern of light or charged particles generated by the lithographic equipment, and reposition the article at another location to again expose the article to the pattern of light or charged particles.
Electron beam lithography is used in the production of high quality patterns. The electron beam passes through magnetic or electrostatic lenses and deflectors capable of directing and focusing the beam onto a wafer or article (reticle) disposed upon a positional stage. An electron beam projection system typically includes an electron beam source, a deflecting system for deflecting the electron beam in a predetermined pattern, and magnetic projection lenses for focusing the electron beam.
During electron beam lithography articles are typically supported and positioned in the xy plane using linear motors that have magnetic assemblies. The xy stages also include an X-guide assembly and a Y-guide assembly that position the article upon actuation of the linear motors. As the guides move during the positioning of the wafer, the magnetic assemblies of the motors as well as magnetic permeable materials associated with the guide assemblies move. As a result, the shifting magnetic fields created by the movement of the magnet assemblies and other magnetic materials interfere with the accurate positioning of the electron beam.
Conventional positioning stages do not shield the electron beam from the shifting magnetic fields created by the moving motors or other moving magnetic permeable components. If not accounted for, the shifting magnetic fields may interact with the electron beam and cause misalignment of the pattern on the article. Thus, it is desirable to provide a positioning stage which minimizes the interaction of the magnetic fields produced by the operation of the stage with the electron beam while exposing the wafer or article. It is also desirable to provide a positioning stage that minimizes vibrations caused by the actuation of the linear motors and movement of the guide assemblies.
This provides a positioning stage system which minimizes the affect of magnetic fields generated by the motors and other moving magnetic permeable components of the positioning stage system on the operating performance of a lithography system. The positioning stage system includes a support platform, an X-direction linear motor and a Y-direction linear motor, an X-member coupled to the X-direction linear motor and to the support platform to move the support platform in an X-direction along a Y-member, wherein the Y-member is coupled to the Y-direction linear motor and to the support platform to move the support platform in a Y-direction along the X-member, and a slide attached to the support platform and slidably engaged with the X-member and the Y-member. The positioning stage system may further include an interferometer to access the coordinate positioning of the support platform, X-member, Y-member, or any combination thereof.
The slide contains an opening adapted to slidably receive the X-member. The slide is also in slidable engagement with the Y-member. The dimensional area in which the slide can move in the X and Y directions is the interior region of the positioning stage system. Preferably, much of the support platform, slide, X-member, and Y-member will be constructed of non-magnetic materials. The non-magnetic materials may include materials selected from ceramics, plastics, carbon fiber, and combinations thereof.
The X-direction linear motor may include a magnet track that is preferably attached to a frame, and a coil member that is preferably attached to the X-member. The Y-direction linear motor may include a magnet track that is preferably attached to a frame, and a coil member that is preferably attached to the Y-member. Preferably, the Y-direction linear motor is disposed in the peripheral region, which is a dimensional area outside the interior region of the positioning stage system.
The positioning stage system may further include a reaction force canceling system for reducing reaction forces produced by the linear motors and/or by the movement of the X-member or the Y-member. Preferably, the reaction force canceling system contains a counter-mass device attached to a frame and disposed at a location coinciding with the center of gravity of the positioning stage system.
The positioning stage system may further include a guide member extending in the Y-direction. Preferably, the guide member is disposed between the support platform and the Y-direction linear motor. It is also preferred that the Y-member contains an end portion with an opening, the guide member extending through the opening of the Y-member. More preferably, the Y-member contains two end portions each with an opening and the guide member contains two generally parallel shafts each extending through one of the openings.
The invention is also directed to an electron beam lithography system that uses the positioning stage system to position an article in an xy plane. The electron beam lithography system includes an electron beam source for generating a beam of electrons, electron beam lenses operable to focus the electron beam onto a surface of an article, deflectors operable to direct the electron beam to specific positions on the article, and the positioning stage system for supporting and positioning the article in an xy plane.
The invention is also directed to a method of moving and positioning an article in an xy plane using the positioning stage system. An article is placed on a support platform, wherein the support platform is attached to a slide that is slidably engaged with an X-member and a Y-member. An X-direction linear motor is actuated, wherein the X-direction linear motor is coupled to the X-member to position the support platform in an X-direction. Preferably, the article is not being exposed as the support platform is moved in the X-direction. A Y-direction linear motor is then actuated, wherein the Y-direction linear motor is coupled to the Y-member to position the support platform in a Y-direction as the article is exposed.